Polyphase electric machines with prefabricated winding layers

ABSTRACT

Known flat winding layers that can be prefabricated and inserted into soft magnetic bodies insufficiently utilize the available space in the grooves and winding overhang of polyphase machines and thus increase the volume and weight of the machine. A new winding design allows high power and force densities to be obtained, thanks to the utilization of the whole available space, and are economic to produce. For that purpose each winding layer (4d) is composed of several conductor lanes (22-24) whose number corresponds to the number of phases. The height of the conductor lanes is reduced at the points (25-33) where they intersect, due to the fact that the conductors are mutually offset, and thus pass over each other inside the layer. By variably adapting the width of the conductor the space in the winding overhang through which the magnetic flow is directed in the soft magnetic body is utilized. The space available in the winding overhangs is completely utilized thanks to double winding layers of which each second layer mirrors the first and is offset by a pole pitch with respect to the first. The winding is suitable for motors and generators whose volume and weight can be advantageously reduced.

TECHNICAL FIELD

The invention concerns a polyphase electric machine with a plane air gapand a soft magnetic body.(37a, 37b, 39a, 39b)

BACKGROUND OF THE INVENTION

In a polyphase rotary field winding for an electric machine in which theconductor lanes are arranged in an offset pattern, hollow spaces usuallyoccur in the winding overhangs, because the conductor lanes of thedifferent phases intersect in the projection from the air gap at leastonce for each pole pitch. This causes the space in the grooves andwinding overhangs to be poorly utilized and the length of the conductorto be increased. If for a high degree of effectiveness a predeterminedlow conductor resistance is to be maintained, the increase of resistancebased on the increased length of the conductor must be compensated by anenlargement of the cross section of the conductor which furtherincreases the volume and weight of the machine.

U.S. Pat. No. 4,398,112 describes a layered conductor for disk armaturesand linear motors in which a conductor lane which is stamped from sheetmetal represents a winding layer which is inserted into the grooves fromthe plane of the groove openings in the direction of the groove depth.By inserting identical winding layers of constant conductor height, theconductor lanes can be cost-effectively punched from sheet metal. Thewinding known from US-PS though shows very short lengths for allconductor lanes; however, since all conductor lanes must have adifferent distance from the plane of the groove openings, spaceutilization in the grooves of a 2-phase machine decreases to 50%, in a3-phase machine to 33.3%, etc. Though the required conductor volumeremains low in the known US-PS, the iron volume of the wielding designthrough which the magnetic flow is passing increases, and with thelarger dimensions of the machine, the volume and weight: of the housingincreases as well.

With the number of phases, however, increases that portion of themachine which actively contributes to the generation of torque. Formachines which are to combine a high degree of effectiveness with highforce and power densities, good space utilization at a higher number ofphases besides a high number of pole pairs and short conductor lengthsis necessary. The share of the housing, of the magnetic yokes, as wellas the exciting winding or, resp. the short circuit cage, or inpermanently excited machines the magnets as part of the total volume ofthe electric machine decrease with increasing groove depth. A highlyefficient electric machine should therefore possess deep grooves forhigh power and force densities.

The invention is, therefore, based on the objective to advance thedevelopment of a polyphase electric machine in which the armature andthe stator lie in a plane opposite to each other which has at least oneslotted soft magnetic body to receive prefabricated winding layers insuch a manner that, even with multiple phases, good utilization ofavailable space is achieved in the grooves and winding overhangs, andwhere the lengths of the conductor lanes can be kept short regardless ofthe depth of the grooves.

SUMMARY OF THE INVENTION

In accordance with the invention, the complete utilization of space inthe grooves of polyphase machines with offset conductor lanes, butparticularly in disk armatures and linear motors, is achieved bydecreasing the cross section of the conductor lanes in the direction tothe groove depth in those sections in which they intersect in theirprojection from the plane of the groove openings. This allowsarrangement of offset conductor lanes belonging to different phases in alayer parallel to the plane of the groove openings. A high utilizationof space in the winding overhangs is achieved by widening the crosssection of the conductor lanes outside of the soft magnetic body.

These changes in the cross section of the conductor keep the length ofthe conductors short and enlarge the conductor cross sections in thewinding overhangs, thereby resulting--via ohmic losses--either in highefficiency or low weight of the machine. In detail, the complete windingconsists of a set of identical winding layers which are stacked indirection to the groove depth. Each winding layer consists ofprefabricated conductor lanes of differing phases.

For descriptive purposes, the conductor lanes are separated intosections in which the sections located inside the soft magnetic body aredesignated as "bars", the sections located in the winding overhang andwhich run in the direction of the groove length are designated as "barconnecting sections", and the sections also located in the windingoverhang but which run in the direction of the groove width aredesignated as "links". One conductor lane or the serial connection ofseveral conductor lanes of the same phase represent a circuit of theelectric machine.

In a favorable embodiment the height of a conductor lane is on theaverage reduced at or shortly after each second passage of the conductorlane from the soft magnetic body into a winding overhang to about onehalf of its height in the grooves. In the resulting space are arrangedlinks of conductor lanes from the same winding layer which, however,belong to a different phase. The links of conductor lanes of a windinglayer are sequentially arranged in the winding overhangs in direction tothe groove length.

The decrease in height of the conductor is largely compensated by thewidening of its cross section--by the width of one tooth face--indirection to the groove width. Sections of the conductor lane that donot intersect in the winding overhang with other conductor lanes of thesame layer can occupy the full height of the layer and, therefore, haveabout twice the cross section compared to the sections in the grooves.In addition to the 100% utilization of space in the grooves, the spacein the winding overhangs can also be utilized at almost 100% for currentconduction, if two winding layers lying on top of each other are set offby one pole pitch and if the cross sections of the conductors in thelinks are adjusted in accordance with the available space in directionto the groove depth.

In accordance with the invention, the conductor lanes of differentphases are arranged at equal distances to the gap surface plane, thenumber of these conductor lanes which together form an self-supportingwinding layer corresponding to the number of phases of the machine. Theproblem of intersection in the winding overhangs is solved by thevariation in the cross sections in which the height of the intersectingconductor lanes of a layer is reduced in such a manner that the sum ofthe height of the conductors correspond to the height of the conductorin the remaining sections of the conductor lane, resp. the layer. Thewinding layer, therefore, is of constant height across its total surfacelying parallel to the gap surface plane, and in stacking several layersto form a larger winding, empty spaces do not ensue.

The connecting paths in the winding overhangs are kept very short byarranging the links as closely to the soft magnetic body as possible andmaking them independent of the groove depth. For high drive voltage andpower the number of serially switched conductor lanes, resp. the numberof the winding layers can be increased arbitrarily depending on thegroove depth, with the length of the individual conductor lanesremaining constant. Since in favorable embodiments all conductor lanesof a phase are identical, manufacturing expense can be kept low.

The width of the conductor lanes increases immediately by the width ofthe tooth face at each passage from the soft magnetic body into thewinding overhang, causing the conductor lanes of adjoining grooves inthe direction to the groove width to abut against each other--separatedonly by a thin insulating layer. By this the space in the windingoverhang which is located in front of the tooth of the soft magneticbody is utilized for current conduction and the conductor cross sectionin the bar connection sections is enlarged, resp. the decrease in theheight of the conductor is compensated.

The conductor lanes in the winding overhangs show short length, becausethey are immediately lead away by the corresponding bar, resp. barconnection section, in direction to the groove width. Only conductorlanes of differing phases which show also in the grooves the samedistance to the gap surface plane and, therefore, form together awinding layer, influence each other in the distribution of space in thewinding overhang. While the length of the conductor and themanufacturing expenses are nearly independent from the depth of thegroove, the losses and expenses connected with the volume of the yokeand magnet are decreasing with increasing groove depth.

If the sum of the lengths of the two bar connection sections which eachadjoin a corresponding bar is equal in all conductor lanes, then theone-piece conductor lanes can be assembled one after another into awinding layer. By this the production of the complete winding issignificantly simplified, because the conductor lanes, independent fromthe remaining assembly, can be shaped into their final form, insulated,and tested. This embodiment is referred to in the description as windingwith asymmetrical winding overhangs.

The embodiment in which the distances of the links from the softmagnetic body in the two winding overhangs are equal for each conductorlane, is referred to in the description as winding with symmetricalwinding overhangs. It also distinguishes itself in that one-piececonductor lanes in their prefabricated form can be joined together intoone winding layer and, if an adhesive was not applied, the compactwinding layer can at any time be disassembled again into its individualconductor lanes. By manufacturing the conductor lanes as single piecesit can be ensured that the conductor lane has the lowest internalresistance in relation to its cross sections and lengths. This is aprerequisite for obtaining favorable efficiency and high power and forcedensities.

If of two identical winding layers which are placed on top of each otherthe upper is mirrored on the gap surface plane and subsequently shiftedby exactly one pole pitch in the direction to the groove width andjoined to the lower layer, and if the height of the links is adapted tothe new available space as well, an embodiment is obtained which ishereafter referred to as double winding layer. In a double windinglayer, at any point on the circumference, a link shares the double layerheight at most with two bar connection sections. The cross sections ofall bar connection sections can now be designed with equal dimensions.This prevents the occurrence of local differences in the generation ofwaste heat on the circumference of the winding overhangs. This design,by complete utilization of the available space in the winding overhangsresults in low resistance which either increases machine efficiency or,via decreased cross sections of the conductors, leads to a lower weight.The avoidance of hollow spaces in the winding layers, between thewinding layers, and between the winding overhang surfaces and thecooling body improves passive heat dissipation.

The structural design as disk armature as well as linear motorrepresents a wide area of application of the invention. On the basis ofthe achievable high force density, a permanently excited disk armatureis particularly suited as direct drive for installation into the wheelrim of a vehicle. In this case, the rotor can be connected with thewheel rim base while allowing for axial displacement which would avoidthe demand on the rotor for bending caused by, e.g., axial forces whichoccur by driving through curves. The cooling body located adjacent tothe winding overhangs and yokes can be designed as supporting elementsof the rim, and the rotor disk as component of a brake. The danger ofbreakage of the powerful magnets is thereby significantly decreased andthe entire wheel rim construction is less rigid and lighter.

If passive cooling is insufficient, winding layers can be replaced inaccordance with a special embodiment by flat radiator sections throughwhich a coolant is circulating, without resulting in an increase of theyoke, magnet, and conductor volume.

The drawings show execution examples of the invention.

FIG. 1 shows an electric machine in accordance with the invention whichis built as disk armature into a wheel rim;

FIG. 2 shows a cut at the line II--II of FIG. 1;

FIG. 3a shows a cut at the line III--III of FIG. 1 through the upperhalf of a complete winding layer for a 12-pole, 4-phase winding withasymmetric winding overhangs;

FIG. 3b shows a cut through the lower hale of the winding layer of FIG.3a;

FIG. 4a shows a conductor lane of FIG. 3;

FIG. 4b shows a conductor lane of a 12-pole, 4-phase winding withsymmetrical winding overhangs;

FIG. 5 shows a cutout during assembly of the three conductor lanes of a3-phase winding layer with asymmetric winding overhangs;

FIG. 6 shows a cutout during assembly of the three conductor lanes of a3-phase winding layer with symmetric winding overhangs;

FIG. 7 shows six segments during assembly into a section of a conductorlane;

FIG. 8 shows the diagram of the conductor lanes and cuts through thelinks of a double winding layer of a 4-phase winding of a linear motor.

FIG. 1 shows the construction of a disk armature with prefabricatedwinding layers built into a wheel rim. The wheel rim is labeled 1, thehead of the rim 1a, and the tire 2. The disk armature itself consists ofthe rotor disk 3 into which are inserted the permanent magnets 3a andthe two halves of the stator 4 and 5. The stator halves 4 and 5 aresupported in relation to the rim 1, respectively the rim base 1b by thebearing 6, and consist each of a soft magnetic body of which only theyoke 4b, 5b is visible in FIG. 1 and the windings 4c, resp. 5c which areshown here in different designs in order to illustrate the invention. Tothe left of the rotor disk 3 is shown a winding 4c with asymmetricwinding overhangs and to the right is shown a winding 5c with doublewinding layers and symmetric winding overhangs.

The rotor disk 3 is connected to the rim base 1b by a pinion in such amanner that the rim 1 is able to move under axial load in order to avoidstress on bending. Here, for example, the rim base may be designed ascage with axially placed slots into which the teeth of the rotor diskare engaging. The axial width of the teeth is less than that of theslots.

The yokes 4b, 5b of the soft magnetic body, as well as the windings 4cand 5c are embedded in the cooling body 8 which essentially functions assupport of the rim base 1b and which is connected with the hub 9. Forpurposes of weight reduction, the hub is designed as a hollow shaft, andit would be possible to install the power electronics into that space upto the rotational axle 7. Within the cooling body are located theconductors for current supply to the individual winding layers by whichcurrent is delivered to the winding layers via commutation equipmentconsisting of a current distributor board 19 and power transistors 11. Adisk brake assembly 12 can be installed into the cooling body itselfwith the brake shoes 12a of the disk brake assembly acting on the rotordisk 3.

FIG. 2 shows a cut at the line II--II of FIG. 1. An armature with fourgrooves per pole pitch is shown. The bars constituting a winding layerare labeled 13a-13d, and accordingly, the bars of the adjacent polepitch 13a'-13d'. In the illustration according to FIG. 2 it can berecognized that the rotor shows pole gaps 3b between the magnet segments3a.

FIG. 3a shows a view in accordance with line III--III of FIG. 1. Herealso the design is a 4-phase winding with asymmetrical winding overhang.The bars inserted into the grooves are again labeled 13a-13d and theyare connected with the bars 13a'-13d' by bar connection sections15a-15d, respectively 15a'-15d', as well as links 14a-14d; link 14a notbeing visible since it lies behind the bar connection sections 15b-15d.Such a unit as shown in FIG. 3a in a top view onto the upper half of thelayer constitutes a winding layer 4d and a complete winding is achievedby axial stacking of several of these winding layers.

FIG. 3b shows the same winding layer 4d as FIG. 3a, however, it depictsa cut through the lower half of the layer. Here, link 14a is visible,but, therefore, not the bar connection sections 15b-15d. The hatching ofthe lower half of the layer is rotated by 90° compared to the hatchingof the upper half of the layer.

FIG. 4a shows a conductor lane of the winding layer from FIG. 3,depicting a winding with asymmetrical winding overhangs in a 4-phasedisk armature with three pole pairs. The teeth of the soft magnetic body4a are symbolized by concentric hatching, while the two windingoverhangs each are indicated by four concentric lines 19, outlining thelimits of the four link areas.

The conductor lane is marked by two hatching patterns, in which thehatching from bottom left to top right designates the upper half 20 ofthe layer and the hatching from bottom right to top left designates thelower half 21 of the layer. Therefore, it can be seen from the type ofhatching in which areas of the conductor lane the full height of thelayer is achieved and in which areas the lower or upper half of thelayers have recesses.

One conductor lane encompasses in the illustrated embodiment the entirecircumference of the machine, minus one pole pitch. This opening is usedeither for current supply 17 and derivation 18 to the drive or, if inthe machine several layers are connected in series, it is used for thetransition to an adjacent conductor lane in direction to the groovedepth. The winding overhang space between the current supply 17 andderivation 18 connections is utilized for supply and derivationconnections to other conductor lanes.

The principle of variable conductor cross sections in the windingoverhangs allows, of course, the realization of alternative conductorlane configurations in which the arrangement of intersections, resp.narrow sections differ from the embodiment thus far presented.

As example of a variation, FIG. 4b shows a conductor lane of a windinglayer from a winding with symmetrical winding overhangs in a 4-phasedisk armature with three pole pairs. Link 16b in the outer windingoverhang shows, in contrast to link 16a of FIG. 4a, the same distance tothe soft magnetic body as the links in the inner winding overhang 16b',resp. 14c. The hatching has the same meaning as in FIG. 4a.

FIG. 5 shows details of the three conductor lanes from a 3-phase windinglayer with asymmetrical winding overhangs. Only that part of eachconductor lane representing two pole pitches is depicted, beginningfictitiously in the middle of their groove in the first pole pitch andending in the middle of the groove of the third pole pitch. The partialpieces depicted as single units belong to conductor lanes from acircular winding layer for a disk armature and, therefore, show bentlinks of differing lengths. The lower conductor lane 22 shows on theleft side, in the area of the links 25, recesses in the upper half ofthe layer and on the right side, in the area of the extended barconnection sections 30, recesses in the upper half of the layer as well.When the middle conductor lane 23 is placed into conductor lane 22, therecesses in the links 25, respectively. 31, and the bar connectionsections 26, resp. 30, complement each other such that both lanes canlie in one plane. The recesses in conductor lanes 22 and 23 furtherallow the insertion of conductor lane 24 in which case the barconnection section 28 due to its reduced height fits into the recessesof the links 25 and 27, and link 33, with its cross section alsoreduced, runs across the bar connection sections 30 and 32.

The conductor lanes in FIG. 6 show in both winding overhangs similarlyconfigured bar connection sections and links. Again, the conductor lanescan simply be slid together in direction of the groove depth by placingthe bar connection sections 38a, 38b of conductor lane 35 which havebeen reduced in their height into the recesses of links 37a, 37b ofconductor lane 34. The recesses of the bar connection sections 40a,respectively. 40b, of conductor lane 36 fit exactly into the space whichis formed by the recesses in links 37a and 39a, resp. 37b and 39b.

Because of the reduced conductor height at the recesses, all threepartial pieces put together result in a sector of a winding layer with aconstant height. Besides the supply segment 43 and the derivationsegment 44 which are shown in FIG. 7 on the bottom right in a specialembodiment, each conductor lane consists, independently of its lengthand its position in the winding layer, of only two different segmentstructures 41 and 42 which, in turn, have been assembled from fourdifferent stamped pieces 41a and 41b, resp. 42a and 42b. The foursegments 41 and 42 depicted in a series from bottom left to top rightare placed in this sequence into an appropriate mold and subsequentlyheated under pressure till they fuse into a one-piece conductor lane.

Another embodiment of the invention represents double winding layerswhich allow for an even and 100% utilization of the winding overhangspace.

FIG. 8a) shows a section of the conductor diagram in a double windinglayer for a 4-phase linear motor in which the section comprises fourpole pitches in a winding overhang. In the drawing of the fictitious cutthe positions of all conductor lanes of the two complementing layers areshown, but for illustrative purposes the widening of the bar connectionsections has been eliminated and a distance is shown between the linkswhich, in reality, should not exist. The conductors in the upper layer45 are more densely hatched and, as in FIG. 3, separated into bars13a-13d, bar connection sections 15a-15d, and links 14a-14d which areindicated by hatching lines that run from bottom left to top right. Thehatching lines of the conductor positions in the lower layer 46 arerotated 90° and, therefore, run from top left to bottom right. FIG. 8a)further clarifies where the cuts B--B, C--C, D--D, and E--E are locatedthat are shown in FIG. 8b, 8c, 8d, and 8e. These drawings of the cutsrepresent the real lateral view of all link layers in a winding overhangof a 4-phase double winding layer. The hatching types correspond tothose used in FIG. 8a. The height of the links corresponds in part,particularly in the outer winding overhang areas, to the doubleconductor height in the grooves, however, the two layers remainidentically shaped.

What I claim is:
 1. Polyphase electric machine with prefabricated winding layers comprising a soft magnetic body with grooves, said grooves having a length, a width and a depth, said machine further having a plane surface parallel to a planar gap, parallel to the plane surface and within said grooves are arranged the winding layers, at least one of said winding layers consisting of at least two conductor lanes of different phases, each of said conductor lanes having a cross section, wherein the conductor cross sections vary on both sides outside the soft magnetic body, and wherein said polyphase electric machine further having a conductor lane of a winding layer, said conductor lane having in partial sections arranged outside the soft magnetic body a smaller cross section parallel to the groove depth than in sections lying inside the soft magnetic body.
 2. Polyphase electric machine with prefabricated winding layers as recited in claim 1 comprising a conductor lane of a winding layer, said conductor lane having partial sections, said partial sections parallel to the groove length, by lying outside the soft magnetic body, and having decreased cross sections in direction to the groove depth, the decrease of said cross sections creating a space in which links of other conductor lanes of the same winding layer are arranged.
 3. Polyphase electric machine with prefabricated winding layers comprising a soft magnetic body with grooves, said grooves having a length, a width and a depth, said machine further having a plane surface parallel to a planar gap, parallel to the plane surface and within said grooves are arranged the winding layers, at least one of said winding layers consisting of at least two conductor lanes of different phases, each of said conductor lanes having a cross section, wherein the conductor cross sections vary on both sides outside the soft magnetic body, and wherein said polyphase electric machine further having a conductor lane of a winding layer, said conductor lane having partial sections parallel to the groove length, but lying outside the soft magnetic body, said partial sections being enlarged in relation to the partial sections which are lying in the soft magnetic body.
 4. Polyphase electric machine with prefabricated winding layers as recited in claim 1, in which conductor lanes of different winding layers are stacked on top of each other in a groove in direction to the groove depth, comprisinga winding layer in which partial sections of conductor lanes are parallel to the groove width, said partial sections of conductor lanes of different phases being arranged parallel to the groove length behind each other and having the same distance to the plane surface.
 5. Polyphase electric machine with prefabricated winding layers as recited in claim 1, comprisingbar connection sections, a sum of said bar connection sections which are connected with a respective bar, being equal for all conductor lanes of a winding layer.
 6. Polyphase electric machine with prefabricated winding layers as recited in claim 1, comprisinga winding layer having conductor lanes with partial sections parallel to the groove width, said partial sections showing on both sides outside the soft magnetic body an equal distance to the soft magnetic body.
 7. Polyphase electric machine with prefabricated winding layers as recited in claim 2, comprising slots provided on said machine through which portions of said soft magnetic body protrude, the conductor lanes being stacked on top of each other in direction to the groove depth in the soft magnetic body and being set off by one pole pitch in relation to each other, each conductor lane being comprised of bars which extend between said slots, and links which connect respective bars, a height of the links parallel to the groove depth corresponding in said partial sections of the links to double the height of the bars.
 8. Polyphase electric machine with prefabricated winding layers as recited in claim 1, said electric machine being designed as a permanent excited disk armature, comprising a rotor disk being directly connected with a wheel rim by a pinion, said pinion transmitting a force without play to the wheel rim.
 9. Polyphase electric machine with prefabricated winding layers as recited in claim 1, comprising a flat cooling element being arranged between two winding layers and being cooled by a coolant which circulates through said cooling element.
 10. A winding layer for use in a polyphase electric machine, the winding layer having two oppositely facing generally flat surfaces that are parallel to one another and a distance between said surfaces taken in a direction normal to said surfaces defines a depth, the winding layer comprising at least two conductor lanes of different phases wherein each conductor lane having portions of which that vary in cross section in a direction parallel to the depth of the winding layer, wherein portions of respective conductor lanes overlap, and wherein the portions of the conductor lanes that overlap have a decreased cross section parallel to the depth of the winding layer.
 11. The winding layer of claim 10 wherein the conducting lanes are sized and configured so as to be generally annular and further to have a plurality of circumferentially spaced slots, in which a soft magnetic body of the electric machine may be disposed through each slot.
 12. The winding layer of claim 11 wherein a portion of only one conducting lane is disposed respectively between two adjacent slots, each conducting lane portion laying between said slots having a selected width generally equal to a distance between said adjacent slots.
 13. The winding layer of claim 12 wherein each said lane further having sections extending arcuately around and outside of said slots, wherein said arcuate conducting lane portions having a decreased cross section in the direction of the depth of the winding layer creating a space in which portions of at least one other conducting lane which extends arcuately around and outside of said slots are disposed.
 14. The winding layer of claim 12 wherein each said lane further having sections extending arcuately around and outside of said slots, wherein at least one of said arcuately extending portions having a width in a direction parallel to said winding layer surfaces that is greater than the width of the portions of the conducting lanes lying between adjacent slots.
 15. The winding layer of claim 12 wherein at least two conducting lanes have portions which extend arcuately and outside of said slots, and wherein the arcuately extending portions of said lanes are adjacent to one another in a radial direction. 